It is well-known to obtain a resin composition, which is generally called a polymer alloy, by incorporating into a thermoplastic resin another resin having different characteristics, as a modifier for the thermoplastic resin. However, when resins inherently incompatible with each other are alloyed, problems, such as phase separation, are likely to occur owing to poor dispersion, frequently rendering it difficult to achieve the objective of the modification. Accordingly, attempts have been made to add various compatibility agents in order to achieve the objective.
For example, with respect to alloying a polyamide and a polyolefin which are incompatible with each other, it is known to use, as compatibility agents, a compound obtained by grafting an unsaturated carboxylic acid or a derivative thereof onto a polyolefin in the presence of a radical initiator; a compound obtained by copolymerizing an olefin monomer with a carboxylic acid or a derivative thereof and then neutralizing the resultant copolymer with a metal salt; a compound obtained by copolymerizing a polyamide with a polyolefin; and the like.
However, conventionally known compatibility agents have not been satisfactory.
For example, U.S. Pat. No. 4,174,358 discloses the use of an elastomer having sites (e.g., carboxylic acid or its derivative) which adhere to a polyamide. However, the elastomer must have a specific value of modulus and is not effective when it is used in a small amount. Further, a polyamide resin composition obtained in accordance with U.S. Pat. No. 4,174,358 has disadvantages in that it undergoes gelation and discoloration into a brown color during the processing thereof.
On the other hand, Japanese Patent Application Laid-Open Specification Nos. 60-1255 and 62-265349 disclose the use of a copolymer or a block copolymer of a polyamide and an olefin polymer. These copolymer and block copolymer are not only commercially disadvantageous in that they are difficult to produce, but also unsatisfactory in effect.